Systems and methods for facsimile echo cancellation

ABSTRACT

The present invention is related to methods and systems for reducing or canceling echoes during fax communications. In an embodiment, during a fax call, a first fax signal from a first fax device intended for a second fax device is detected. Based at least in part on detecting the first fax signal from the first fax device or on the termination of the first fax signal, an echo audio packet is muted, wherein the echo audio packet is at least partly the result of the first fax signal being transmitted over a network, the network including at least a data network.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention is related to telecommunications, and inparticular to echo management or cancellation in an Internet Protocolcommunications network.

2. Description of the Related Art

The use of Fax over Internet Protocol (FoIP) has become increasingpopular. One reason for the increasing popularity of FoIP is thepotential for significant reductions in facsimile related costs.

However, certain technical challenges are posed to systems using FoIP.For example, echoes can interfere with FoIP performance. There areseveral forms and causes of echo in the Public Switched TelephoneNetwork (PSTN). For example, an echo can be caused by poor qualityanalog and digital telecommunication terminals (handsets, fax machines,etc.). An echo can be caused by background noise of the caller andcalled party. In addition, an echo can be caused by signal reflectionsgenerated by a circuit that converts between a 4-wire circuit, whichincludes two transmit wires and a 2-wire circuit, that includes onetransmit wire and one receive wire.

In many instances, echo is not a very serious problem with aconventional PSTN-based fax communication, as roundtrip delays aretypically less than 50 ms. However, echo becomes a serious problem whena packet switched system is used in the communications path, such as inFax-over-Internet Protocol (FoIP) networks, because the round-trip delaythrough the network is often greater than 50 ms. This echo interfereswith the Fax T.30 and T.4 protocols used by fax machines/servers toestablish a call.

SUMMARY OF THE INVENTION

The present invention is related to telecommunications, and inparticular to echo management or cancellation in a communicationsnetwork that includes a data network, such as the Internet.

One embodiment provides a method of canceling echoes associated with faxsignaling over a network including at least a data network, during a faxcall, the method comprising: during the fax call, detecting a first faxsignal from a first fax device intended for a second fax device;detecting the first fax signal from the first fax device and/or thetermination of the first fax signal; muting an echo audio packet basedat least in part on detecting the first fax signal from the first faxdevice and/or the termination of the first fax signal, wherein the audiopacket is an echo of the first fax signal being transmitted over anetwork, the network including at least a data network.

Another embodiment provides a fax system, comprising: a data networkinterface; and a line conditioner system coupled to a data network viathe data network interface and further coupled to a fax device, whereinthe line conditioner system is configured to detect when a first faxsignal is generated by the fax device and/or to detect when the firstfax signal terminates, and based at least in part on detecting when thefirst fax signal is generated and/or when the first fax signalterminates, mute a packet directed to the first fax device and receivedat the line conditioner circuit via the data network if the packet isreceived during a selected first period of time.

Still another embodiment provides a method of processing fax signalingcarried over a network including at least a data network, the methodcomprising: monitoring a first fax signal from a first fax systemdirected to a second fax system; and based at least in part upon themonitoring of the first fax signal from the first fax system, muting anaudio packet directed to the first fax system, wherein the audio packetis at least partly the result of the first fax signal being transmittedover a network, the network including at least a data network.

BRIEF DESCRIPTION OF THE DRAWINGS

Exemplary embodiments of an echo cancellation and management system areillustrated in the accompanying drawings, which are for illustrativepurposes only. The drawings comprise the following figures, in whichlike numerals indicate like components.

FIG. 1 illustrates an example FoIP system and a fax call process.

FIG. 2 illustrates another example FoIP system.

FIG. 3 illustrates another example FoIP system.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The present invention is related to telecommunications, and inparticular to echo management or cancellation in a packet communicationsnetwork. In many conventional FoIP systems echo can be a seriousproblem, because the round-trip delay through the packet network viawhich faxes are delivered is often greater than the typical guard window(e.g., 75 ms) used to ignore such echoes, and hence the echo may beinterpreted by a fax system involved in the fax communication (e.g., areceiving fax server or fax machine) as an error condition. Upondetermining that the echo is an error condition, the fax system may dropthe call. As will be described below with respect to certain exampleembodiments, echo cancellation and management processes are provided toavoid such dropped calls. For example, in one embodiment a packetnetwork latency is estimated, and using that estimate, a mute periodand/or start time is determined, wherein a fax signal echo (e.g., theecho can be of a fax handshaking signal) is anticipated. An audio signalis selectively muted during the mute period to thereby prevent the echofrom being received by the fax system.

While the following description relates to an embodiment utilizing theInternet and related protocols, other networks other protocols may beused as well. Further, while certain protocols, such as IP and RTP, andstandards, such as T.37 and T.38, are referred to, the present inventionis not limited to use with these protocols and standards, or with anyparticular version of these protocols or standards.

The functions described herein are optionally performed by executablecode and instructions stored in computer readable memory and running onone or more computers equipped with networking devices. However, thepresent invention can also be implemented using state machines, signalprocessing chips, and/or hardwired electronic circuits. Further, withrespect to the example processes described herein, not all the processstates need to be reached, nor do the states have to be performed in theillustrated order. Further, certain process states that are described asbeing serially performed can be performed in parallel, and certainprocesses that are described as being performed in parallel can beperformed serially.

An example sequence of establishing a fax call is described below andshown in FIG. 1. This example includes a fax machine 200 thatcommunicates with a call manager 202 over a network 203, such as theInternet or other packet network. The call manager 202 optionallyincludes a fax server capable of originating or receiving voice and/orfax calls over PSTN or Internet Protocol (IP) networks, and so the callmanger 202 will sometimes be referred to as fax server 202. However,rather than using a server-based system, optionally, the call manager isor includes a conventional or other type of fax machine or fax receiver.

The fax server 202 is optionally compatible with one or moreFoIP-related standards, such as the real-time network standard (T.38)and the store-forward FoIP network standard (T.37). The fax server 202can optionally be connected directly to a packet network, such as theInternet, via a network interface circuit, and can transmit mediastreams via real time protocol (RTP) packets.

The fax machine 200 and/or the fax server 202 optionally include modems,such as high speed modems, used to transmit fax data. The modem convertsdigital data generated by the fax machine or fax server into analogsignals for transmission over analog lines.

The fax machine 200 can be optionally coupled to a Media Gateway (MG)over the PSTN as shown in FIG. 3. A MG enables the transmission ofcombined voice and data over the packet network. The MG converts anincoming circuit-switched call into digital data for transmission overthe packet network (e.g., IP network) and reconverts digital datadirected to the fax machine 200 to a circuit-switched call. A fax servercan similarly be coupled to a FoIP MG.

At state 100, fax machine 200 places a call which is directed to the faxserver 202. The call can be manually placed by a human user at faxmachine 200 initiating a call (e.g., by dialing a corresponding number,by selecting a name from an electronic directory, or otherwise) to thecall manager or fax server 202 and placing fax machine 200 into faxmode, or the call can be placed automatically, without humaninteraction. The answering fax machine or fax server 202 answers thecall at state 104 and returns an answer tone (e.g., a CallEd stationIdentification (CED)) at state 106. For example, the CED can be a toneat a predetermined frequency, such as 2.1 kHz, such as is generated by areceiving Group 3 fax machine.

If the call is automatically dialed, the fax machine 200 will alsoindicate the fax call with a calling tone (CNG) at state 102, which canbe a short, periodic tone that begins immediately after the number isdialed. These tones can be used to allow a human participant to realizethat a machine, such as a fax machine, is present on the other end ofthe call.

The control and capabilities exchange (CCE) phase of the fax call isused to identify the capabilities of the fax machine at the other end ofthe call. During the CCE phase, the communicating devices (e.g., two faxmachines or a fax machine and a call manager) also negotiate theacceptable conditions for the call. The exchanges of control messagesduring the fax call are optionally sent using a rate that most faxmachines support, such as by using the low-speed (300 bps) modulationmode in a half-duplex mode (one talker at a time). A control message ispreceded by a preamble, such as a one-second preamble, which allows thecommunication channel to be conditioned for reliable transmission.

At state 108 the called fax server 202 starts the process by sending aDigital Identification Signal (DIS) message, which contains thecapabilities of the fax server 202. An example of a capability thatcould be identified in this message is the support of the V.17 (14,000bps) data signaling rate. At this time, the called subscriberinformation (CSI) and NonStandard Facilities (NSF) messages areoptionally also sent. NSF are capabilities or enhancements that aparticular fax manufacturer has built into a fax machine.

Once the calling fax machine 200 receives the DIS message, the faxmachine 200 determines the conditions for the call by examining itscapabilities table. The calling fax machine 200 responds at state 110with the Digital Command Signal (DCS), which defines the conditions ofthe call. For example, the DCS can inform the fax server 202 whichcapabilities were selected and can lock the receiving unit into the faxserver 202 into the selected capabilities.

At this stage, high-speed modem training begins. The high-speed modem isused to transfer page data and converts digital data into analog signalsfor transmission over analog lines. The calling fax machine 200 at state112 sends a Training Check Field (TCF) through the modulation system toverify the training and to ensure that the channel is suitable fortransmission at the accepted data rate. The called fax server 202responds at state 114 with a confirmation to receive (CFR) signal, whichindicates that capabilities and the modulation speed have been confirmedand that the fax page may be sent.

The confirming CFR sent from the fax server 202 is received by the faxmachine 200, but enough of the signal may bounce or reflect off the farend as echo to interfere with the initial burst of fax data representingthe first fax page (e.g., the first fax page of scanned in andcompressed data), which begins at state 116.

In the Public Switched Telephone Network, latency is low enough that anecho is ignored during a standard 75 ms guard window after sending ofthe CFR from the fax server 202. However, in a FoIP environment, latencyfrom 80-120 ms causes enough of a time shift that the signal echoarrives after the guard window of 75 ms. When the echo arrives at thereceiving fax server 202, the fax server 202 has changed state and isnow listening for the first page of the fax. The echo CFR is not the faxdata (V.29 signal) the fax server 202 expects, and so the echo may beinterpreted as an error condition, whereupon the fax server 202 mayprematurely drop the call.

Optionally, to reduce or eliminate dropped calls as a result of an echoCFR, the call manager 202 includes or is coupled to an echo managementor cancellation line conditioner system 204. For example, the echocancellation can be performed by software executing on the call managerfax server 202, or can be dedicated hardware (e.g., a digital signalprocessor-based system). In another embodiment, an example of which isillustrated in FIGS. 2 and 3, the call manager 202 is coupled to an echocancellation line conditioner system placed in the path between the callmanager 202 and the fax machine 200. An example embodiment of an echocancellation line conditioner system will be discussed in greater below.

FIG. 2 illustrates an example embodiment, wherein the echo cancellationline conditioner system 204 is placed in the path between the callmanager 202 and the fax machine 200. The fax machine 200 is coupled tothe packet network 203 via the PSTN 205.

The echo cancellation line conditioner system 204 can include a server.The echo cancellation line conditioner system 204 conditions the networkpath in a FoIP environment in order to eliminate the echo which wouldotherwise cause a fax call to be dropped, or to reduce the echo so thatit does not result in dropped calls. The echo cancellation lineconditioner system server 204 can be a server separate from the callmanager server 202, or the server 204 can be a software applicationhosted in the call manager server 202.

The echo cancellation line conditioner system server 204 monitors theReal Time Protocol (RTP) media stream from the fax server 202 foroutbound audio (e.g., by detecting which packets have associated audioenergy. If audio is detected originating from the fax server 202, thenafter a delay (e.g., a predetermined delay or a variable window), theserver 204 mutes the inbound audio signal from the original sending faxmachine 200 (or in this case, the echo signal reflected back from thefax machine 200 or the path thereto, that appears to be an inboundsignal from fax machine 200). By way of example, the muting process canbe performed by suppressing the outbound audio packets, and/or the audiopackets can be substituted with silence audio packets (e.g., audiopackets having no or a very low associated audio volume).

The delay can be set or selected to correspond to an estimated networklatency, such as a measured packet network path latency with respect toone or more paths between the fax server 202 and the fax machine 200.The estimated latency can optionally also include PSTN and other pathlatencies. By way of example, the delay can be 80 ms, 90 ms, 100 ms, 110ms, 120 ms, 130 ms or other appropriate delay time. In one embodiment,several measurements are taken of IP network path latencies, and theaverage latency, or other statistical latency estimation, is used todetermine the delay. When the server 204 detects the termination of theoutbound audio signal (e.g., by detecting the lack of speech energy orsilence) from fax server 202, the server 204 waits the selected or setdelay period and then opens the audio path to the original sending faxmachine 200. Optionally, instead, or in addition, the delay period canbe based on when the audio was generated by the server 204.

In this example, the server 204 is in the network IP path for theduration of the fax call. The subsequent fax call states including pagetransfer, end of page and multipage signaling, and call release, areperformed as appropriate.

One or more processes can be utilized to measure latencies, such as thelatencies in IP or other packet networks over which the FoIPcommunication will be performed, wherein the latency measurements can beused to set the delay after which a the server 204 mutes the audiosignal. For example, an ICMP (Internet Control Message Protocol) EchoRequest packet, also known as a ping, is transmitted directly from thefax server 202 to the target (e.g., the media gateway where the inboundfax call is converted from a PSTN call to a VoIP call) to be tested. Thetarget, upon receipt of the ICMP Echo Request, builds a correspondingICMP Echo Reply packet and transmits it back to the fax server that sentthe Echo Request. The time between the transmittal of the Echo Requestand the receipt of the Echo Reply will provide the fax server with anindication of the communication latency. Optionally, a traceroute(tracert) routine can also provide an approximation of the latency.

Latency can be measured using still other processes. For example, a TestTCP (TTCP) utility can be used to measure TCP (transmission controlprotocol), or UDP (user datagram protocol) throughput through the IPpath between the fax server 202 and the media gateway where the inboundfax call is converted from a PSTN call to VoIP. The fax server 202 sendsa specified number of TCP (or UDP) packets to the media gateway. At theend of the test, the two sides provide the number of bytes transmittedand the time elapsed for the packets to pass from one end to the other.These figures can be used to calculate the actual or estimatedthroughput and latency on the link. Other tools, such as pchar, can alsobe used to measure latency and throughput.

By way of further example, test calls can be placed from a fax servervia the PSTN to the fax machine phone number. The call routes throughthe IP network and terminates at the fax machine. When the call isconnected, tones (e.g., fax handshaking tones or DTMF tones) can beexchanged. The timing of this exchange, which is the time between a senttone and receipt of a reply tone, gives an estimated measure of thelatency.

FIG. 3 shows a more detailed description of example components used inan example integrated PSTN and IP network. The fax machine 200 iscoupled to the PSTN 205 via a Class 5 switch 208. The Class 5 Switch 208is communicates with a Session Initiation Protocol (SIP) component 206using the SS7 signaling protocol. SIP is a signaling protocol which canbe used for Internet conferencing, telephony, presence, eventsnotification and instant messaging, by way of example. The SIP componentis coupled to a soft switch 212 of an IP provider 210 and communicatesvia SS7 signaling. The soft switch 112 manages the service logistics ofthe traffic between the IP provider 210 and the PSTN 205. The softswitch is coupled to a media gateway 214 which converts circuit-switchedvoice to packet-based traffic. The media gateway 214 is coupled to thePSTN 205 via one or more trunks.

As can be seen in this figure, the line conditioning functions performedby server 204 pertain to the RTP streams communicated over the pathbetween the call manager 202 and the media gateway 214. Optionally, theserver 204 does not perform echo cancellation for the signaling betweenthe Call Manager 202 and SIP proxy 218.

The soft switch 210 is further coupled to a proxy 216. The proxy 216 iscoupled via an IP or other packet network 203 to the SIP proxy 218associated with a call processing system 220. The media gateway 214 iscoupled to the line conditioner 204 over the network 203. The callmanager (including the fax server) 204 is coupled to the proxy 218 andthe line conditioner 204.

Although this invention has been described in terms of a simple andpreferred embodiment, other embodiments that are apparent to those ofordinary skill in the art are also within the scope of this invention.For example, the conditioning server 204 could automatically adapt theecho suppression by correlating the outbound signal with the returnsignal. In another embodiment, the conditioning server could listen forand mute only specific frequencies based on the state of the call andthe audio signal generated by the fax server 202.

1. A method of canceling echoes associated with fax signaling over anetwork including at least a data network, during a fax call, the methodcomprising: during the fax call, detecting a first fax signal from afirst fax device and/or the termination of the first fax signal, whereinthe first fax signal is intended for a second fax device; muting an echoaudio packet based at least in part on detecting the first fax signalfrom the first fax device and/or the termination of the first faxsignal, wherein the audio packet is an echo of the first fax signalbeing transmitted over a network, the network including at least a datanetwork.
 2. The method as defined in claim 1, wherein the audio packetis in a real time protocol stream.
 3. The method as defined in claim 1,wherein the data network is the Internet.
 4. The method as defined inclaim 1, wherein the muting is performed by intercepting the audiopacket, and preventing the audio packet from reaching the first faxdevice.
 5. The method as defined in claim 1, wherein the muting isperformed at least in part by intercepting the echo audio packet, andsubstituting the echo audio packet with an audio packet corresponding tosilent audio.
 6. The method as defined in claim 1, wherein the first faxdevice is a fax server.
 7. The method as defined in claim 1, wherein thesecond fax device is a dedicated fax machine.
 8. The method as definedin claim 1, wherein the muting is performed at least 80 ms aftertermination of the first fax signal.
 9. The method as defined in claim1, wherein the muting is performed within a window beginning at least 80ms after termination of the first fax signal, and ending 120 ms aftertermination of the first fax signal.
 10. The method as defined in claim1, wherein the wherein the muting is performed during a window periodselected based at least in part on a plurality of network latencymeasurements.
 11. The method as defined in claim 1, wherein the whereinthe muting is performed during a window period selected based at leastin part on network latency for at least a portion of the network betweenthe first fax device and the second fax device.
 12. The method asdefined in claim 1, further comprising measuring network latency. 13.The method as defined in claim 1, further comprising measuring networklatency using one or more of a ping, a test TCP operation, or a toneexchange.
 14. The method as defined in claim 1, wherein the echo audiopacket results from a confirmation to receive (CFR) signal echo.
 15. Themethod as defined in claim 1, wherein the second fax device is coupledto a gateway that converts a circuit switched call into digital data fortransmission over the data network.
 16. The method as defined in claim1, wherein the first fax device is coupled directly to the data networkvia a network interface circuit.
 17. The method as defined in claim 1,wherein the second fax device initiates the fax call to the first faxdevice.
 18. A fax system, comprising: a data network interface; and aline conditioner system coupled to a data network via the data networkinterface and further coupled to a fax device, wherein the lineconditioner system is configured to detect when a first fax signal isgenerated by the fax device and/or to detect when the first fax signalterminates, and based at least in part on detecting when the first faxsignal is generated and/or when the first fax signal terminates, mute apacket directed to the first fax device and received at the lineconditioner circuit via the data network if the packet is receivedduring a selected first period of time.
 19. The fax system as defined inclaim 18, wherein the fax device is a fax server or a dedicated faxmachine.
 20. The fax system as defined in claim 18, wherein the lineconditioner system further comprises a server.
 21. The fax system asdefined in claim 18, wherein the line conditioner system mutes thepacket by preventing the packet from reaching the fax device.
 22. Thefax system as defined in claim 18, wherein the packet is an audio packetresulting from an echo of the first fax signal.
 23. The fax system asdefined in claim 18, further comprising a gateway coupled to the lineconditioner system, wherein the gateway converts digital data from theline conditioner system to a circuit-switched call.
 24. The fax systemas defined in claim 18, wherein the first period of time begins at least80 ms after the first signal is generated.
 25. The fax system as definedin claim 18, wherein the first period of time is at least 40 ms long.26. The fax system as defined in claim 18, wherein the first fax signalis a confirmation to receive (CFR) signal.
 27. The fax system as definedin claim 18, wherein the first fax signal is a handshaking signaldirected to a second fax device.
 28. The fax system as defined in claim18, further comprising the fax device.
 29. A method of processing faxsignaling carried over a network including at least a data network, themethod comprising: monitoring a first fax signal from a first fax systemdirected to a second fax system; and based at least in part upon themonitoring of the first fax signal from the first fax system, muting anaudio packet directed to the first fax system, wherein the audio packetis at least partly the result of the first fax signal being transmittedover a network, the network including at least a data network.
 30. Themethod as defined in claim 29, wherein the audio packet is in a realtime protocol stream.
 31. The method as defined in claim 29, wherein thedata network is the Internet.
 32. The method as defined in claim 29,wherein the muting is performed by a line conditioner system thatreceives the audio packet, and prevents the audio packet from beingreceived by the first fax system.
 33. The method as defined in claim 29,wherein the muting is performed at least in part by receiving the audiopacket before it is received by the first fax system, and substitutingthe audio packet with another packet.
 34. The method as defined in claim29, wherein the first fax system includes a fax server and/or adedicated fax machine.
 35. The method as defined in claim 29, whereinthe muting is performed at least 80 ms after the first fax signal isgenerated.
 36. The method as defined in claim 29, wherein the fax signalis a handshaking signal transmitted by the first fax system prior to thesecond fax system transmitting an initial fax page in a fax callassociated with the first fax signal.
 37. The method as defined in claim29, wherein timing for the muting of the audio packet is selected basedat least in part on a plurality of network latency measurements.
 38. Themethod as defined in claim 29, wherein timing for the muting of theaudio packet is selected based at least in part on network latency forat least a portion of the network between the first fax system and thesecond fax system.
 39. The method as defined in claim 29, furthercomprising: measuring network latency, and using the measured networklatency to determine muting timing.
 40. The method as defined in claim29, further comprising: measuring network latency using one or more of aping, a test TCP operation, or a tone exchange; and using the measurednetwork latency to determine muting timing.
 41. The method as defined inclaim 29, wherein the audio packet is the result of an echo of the firstfax signal.
 42. The method as defined in claim 29, wherein the secondfax system is coupled to a gateway that converts a circuit switched callinto digital data for transmission over the data network.
 43. The methodas defined in claim 29, wherein the first fax system is coupled directlyto the data network via a network interface circuit.
 44. A method ofcanceling echoes associated with fax signaling over a network includingat least a data network, the method comprising: during the fax call,detecting a first fax signal from a first fax device intended for asecond fax device; muting an audio packet based at least in part ondetecting the first fax signal from the first fax device and/ortermination of at least one fax signal, wherein the audio packetincludes an echo of the at least one fax signal being transmitted over anetwork, the network including at least a data network.
 45. The methodas defined in claim 44, wherein the audio packet is in a real timeprotocol stream.
 46. The method as defined in claim 44, wherein the datanetwork is an Internet Protocol network.
 47. The method as defined inclaim 44, wherein the second fax device is configured to participate ina fax call over an Internet Protocol (IP) network.
 48. The method asdefined in claim 44, wherein the second fax device is configured toparticipate in a fax call over a switched telephone network.
 49. Themethod as defined in claim 44, wherein the second fax device isconfigured to participate in a voice call over a switched telephonenetwork.
 50. The method as defined in claim 44, wherein the muting isperformed by intercepting the audio packet, and preventing the audiopacket from reaching the second fax device.
 51. The method as defined inclaim 44, wherein the muting is performed at least in part byintercepting the audio packet, and substituting the audio packet with adifferent audio packet corresponding to silent audio.
 52. The method asdefined in claim 44, wherein the second fax device is a voice and faxprocessing system.
 53. The method as defined in claim 44, wherein themuting is performed during a period selected based at least in part on aplurality of network latency measurements.
 54. The method as defined inclaim 44, wherein the wherein the muting is performed during a periodselected based at least in part on network latency for at least aportion of the network between the first fax device and the second faxdevice.
 55. The method as defined in claim 44, further comprisingmeasuring network latency.
 56. The method as defined in claim 44,further comprising measuring network latency using a ping, a test TCPoperation, and/or a tone exchange.
 57. The method as defined in claim44, wherein the second fax signal is a confirmation to receive (CFR)signal.
 58. The method as defined in claim 44, wherein the audio packetresults from a confirmation to receive (CFR) signal echo.
 59. The methodas defined in claim 44, wherein the at least one fax signal is atraining-related signal.
 60. The method as defined in claim 44, whereinthe first fax device is coupled to a gateway that converts a circuitswitched call into digital data for transmission over the data network.61. The method as defined in claim 44, wherein the second fax device iscoupled directly to the data network via a network interface circuit.62. The method as defined in claim 44, wherein the first fax deviceinitiates the fax call to the second fax device.
 63. A line conditionersystem, comprising: a first interface configured to communicate data viaa data network; and a second interface configured to communicate withone or more fax devices, wherein the line conditioner system isconfigured to detect at least one fax signal generated by at least onefax device and/or to detect the termination of at least one fax signal,wherein the at least one fax signal is transmitted at least in part overthe data network, and based at least in part on such detection, and tomute at least one packet directed to at least one fax device, whereinthe at least one packet is received at the line conditioner system viathe data network.
 64. The line conditioner as defined in claim 64,wherein the line conditioner system further comprises a network server.65. The line conditioner as defined in claim 64, wherein the datanetwork is an Internet Protocol network.
 66. The line conditioner asdefined in claim 64, wherein the line conditioner system mutes thepacket by preventing the packet from reaching the at least one faxdevice.
 67. The line conditioner as defined in claim 64, wherein thepacket is an audio packet resulting from an echo of the at least one faxsignal.
 68. The line conditioner as defined in claim 64, furthercomprising a gateway, wherein the gateway converts digital data from theline conditioner system to a circuit-switched call.
 69. The lineconditioner as defined in claim 64, wherein the at least one fax signalis a confirmation to receive (CFR) signal.
 70. The line conditioner asdefined in claim 64, wherein the at least one fax signal is ahandshaking signal directed to a first fax device.
 71. The lineconditioner as defined in claim 64, further comprising the at least onefax device.
 72. The line conditioner as defined in claim 64, wherein themuting is performed during a period selected based at least in part on aplurality of network latency measurements.
 73. The line conditioner asdefined in claim 64, wherein the muting is performed at least in part byintercepting an audio packet, and substituting the audio packet with anaudio packet corresponding to silent audio.
 74. A method of processingfax signaling over a network including at least a data network, themethod comprising: monitoring a fax signal from a first fax systemdirected to a second fax system; and based at least in part upon themonitoring of the fax signal from the first fax system, muting an audiopacket that would otherwise be received by the first fax system, whereinthe audio packet is at least partly the result of the fax signal beingtransmitted over a network, the network including at least a datanetwork.
 75. The method as defined in claim 74, wherein the audio packetis in a real time protocol stream.
 76. The method as defined in claim74, wherein the data network is an Internet Protocol network.
 77. Themethod as defined in claim 74, wherein the muting further comprises:receiving the audio packet at a line conditioner system; and preventingthe audio packet from being received by the first fax system.
 78. Themethod as defined in claim 74, wherein the muting is performed at leastin part by receiving the audio packet before it is received by the firstfax system, and substituting the audio packet with another packet. 79.The method as defined in claim 74, wherein the muting is performed 80 msor more after the fax signal is generated.
 80. The method as defined inclaim 74, wherein the fax signal is a handshaking signal transmitted bythe first fax system prior to the second fax system transmitting aninitial fax page in a fax call associated with the fax signal.
 81. Themethod as defined in claim 74, wherein timing for the muting of theaudio packet is selected based at least in part on a plurality ofnetwork latency measurements.
 82. The method as defined in claim 74,wherein timing for the muting of the audio packet is selected based atleast in part on network latency for at least a portion of the networkbetween the first fax system and the second fax system.
 83. The methodas defined in claim 74, further comprising: measuring network latency;and using the measured network latency to determine muting timing. 84.The method as defined in claim 74, further comprising: measuring networklatency using one or more of a ping, a test TCP operation, or a toneexchange; and using the measured network latency to determine mutingtiming.
 85. The method as defined in claim 74, wherein the audio packetis the result of an echo of the fax signal.
 86. The method as defined inclaim 74, wherein the second fax system is coupled to a gateway thatconverts a circuit switched call into digital data for transmission overthe data network.
 87. The method as defined in claim 74, wherein thefirst fax system is coupled directly to the data network via a networkinterface circuit.